1. Field of the Invention
This invention relates to a hermetically sealed chip carrier including a lead frame for use with an electrically erasable programmable read only memory (EEPROM) chip.
2. Description of the Prior Art
The manufacture of lead frames is disclosed in, for example, U.S. Pat. Nos. 4,204,317; 4,137,546; 3,750,277; 3,537,175; and 3,469,953. Typically a chip is mounted on a lead frame, electrically connected to the leads thereof, and packaged. Examples of such structure are described in U.S. Pat. Nos. 4,744,009; 4,727,221; 4,691,225; 4,663,651; 4,663,650; 4,635,165; 4,326,214; 4,135,038; 4,105,861; 3,943,623; 3,874,549; 3,660,819 and 3,404,215.
Typically, an EEPROM chip is packaged in a hermetically sealed ceramic package, known in the art as a "CERDIP" package, which incorporates an ultra violet (UV) transparent glass or quartz window. In the manufacture of such structures relatively high temperatures are required in the sealing operation and this results in reduced yields. Such a ceramic package tends to be inherently expensive. In addition, typical transparent covers heretofore used in CERDIP packages have been quartz in ceramic, which is expensive. Further, the use of ceramic covers has inhibited variation in size and shape of the window, the traditional window being formed from extruded quartz bars which are sliced for use in the ceramic cover.
It is an object of this invention to produce an EEPROM chip carrier which can be hermetically sealed to relatively low temperatures thereby increasing yields and reducing costs. A further object is to provide an EEPROM chip carrier using materials which are less expensive and easier to work than ceramic. It is also an object to provide an EEPROM carrier the UV transparent window of which can be readily varied in size and shape to accommodate any chip such as, for example, the relatively larger chips presently being used.